Our Mite Inhabitants!

Mites on our face

You’ll be as amazed (and disgusted) as I was after reading this post, did you know you have microscopic animals living on your face? Yes, they spend their entire lives on the face, where they eat, mate and finally die.

There are two species of mite that live on your face: The Demodex Folliculorum and the D Brevis. Demodex mites have eight short and stubby legs near their heads. Their bodies are elongated, almost worm-like. Under a microscope, they look as though they’re swimming through oil, neither very far, nor very fast. They’re very sluggish. In other words think of them as insects and spiders, anthropods with 8 legs. The D Brevis are very similar, under normal conditions they are not harmful, and are considered to be commensals (the mite benefits but there is no harm or benefit to the host) rather than parasites.

The two species live in slightly different places though, the D. Folliculorum reside in pores and hair follicles, while D. brevis prefers to settle deeper, in your oily sebaceous glands.

Although her face seems flawless, there are Demodex living on her face.

In 2014, North Carolina State University found that about 14% of people had visible mites, but for everyface, there was some trace of the mites.

A Demodex folliculorum under a light microscope

It’s not clear what the mites are getting from us. For starters, we’re not sure what they eat. “Some people think they eat the bacteria that are associated with the skin,” says Thoemmes. “Some think they eat the dead skin cells. Some think they’re eating the oil from the sebaceous gland.” Thoemmes and her colleagues are currently looking at the microorganisms that live in the mites’ guts. That could help determine their diet.

There’s also not much about how much they reproduce either. Other species of mite get up to all sorts of things, from incest and sexual cannibalism to matricide and fratricide. But so far it seems Demodex are a little less extreme. “It appears that they come out at night to mate and then go back to their pores.” So if there’s one thing we know, it’s wash your face in the morning!

The heads and legs of Demodex folliculorum

Female Demodex mites lay their eggs around the rim of the pore they are living in but they probably don’t lay many. “Their eggs are quite large, a third to a half the size of their body, which would be very metabolically demanding. They’re so large they’re probably laying one at a time.” There is a video available on YouTube of a Demodex laying eggs: click here

A Demodex folliculorum under a scanning electron microscope

It’s also been noticed that they do not have an anus, all their waste builds up over time and then there’s one large flush of bacteria..

“I would think that they’re not harming us in a way that’s detectable,” says Thoemmes. “If we were having a strong negative response to their presence, we’d be seeing that in a greater number of people.”

The one thing they have been linked to is a skin problem called rosacea. This mainly affects people’s faces, and begins with flushing before sometimes progressing to permanent redness, spots, and sensations of burning or stinting. Studies have found that people suffering from rosacea tend to have more Demodex mites. Instead of 1 or 2 per square centimetre of skin, the number rises to 10 to 20.

Human skin, with sebaceous glands attached to hair follicles

There may also be a link with the immune system, which normally protects us against infections. Thoemmes says the mites have been found to be particularly abundant on people with immune deficiencies, such as AIDS or cancer.

It’s still not clear what sort of relationship we have with our Demodex mites. We can be sure they are not parasites, which take things from us and cause harm in the process. The relationship might instead be commensal, meaning that they do take something from us but not in a way that normally causes harm. For most people, most of the time, they’re harmless. They may even be beneficial. For instance, they may clear dead skin off our faces or eat harmful skin bacteria.

But suppose you really wanted to get rid of them. Could you?

It looks as if there is something special on our faces that they need. Even if you kill them off, you’re going to get them again, because they’re everywhere and they want to be on your face.

The mites could reveal a lot about our relationships with each other. Their genes contain clues to our history. When Thoemmes looked at the mites’ DNA, she found that mites collected from Chinese populations were distinctly different from those collected from North and South American populations. Because these differences exist, studying the mites could tell us how our distant ancestors migrated around the planet, and reveal which modern populations are most closely related. “We might be able to figure out human associations… we weren’t able to figure out or see before,” says Thoemmes. She is particularly interested in finding out about the colonisation of Central and South America. “There’s been a lot of speculation as to which populations of humans colonised Brazil and inter-bred.”

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Eyelashes, with D. folliculorum lurking in the follicles

For now, this is all speculation. But even if none of these ideas pay off, the story of Demodex is a reminder that we humans are home to a multitude of species.

Some, such as head lice and fleas, hop aboard occasionally, or only live on certain populations. Others, like Demodex and the microorganisms in our guts, are with all of us throughout our lives. Our bodies are seething with microorganisms: they make up 90% of our cells.

There is a simple lesson here. You are not just you: you are a walking, talking community, an entire ecosystem held within one body.

Research based on a BBC Articles

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